Beta-amino heterocyclic dipeptidyl peptidase inhibitors for the treatment or prevention of diabetes

ABSTRACT

The present invention is directed to compounds which are inhibitors of the dipeptidyl peptidase-IV enzyme (“DP-IV inhibitors”) and which are useful in the treatment or prevention of diseases in which the dipeptidyl peptidase-IV enzyme is involved, such as diabetes and particularly type 2 diabetes. The invention is also directed to pharmaceutical compositions comprising these compounds and the use of these compounds and compositions in the prevention or treatment of such diseases in which the dipeptidyl peptidase-IV enzyme is involved.

BACKGROUND OF THE INVENTION

Diabetes refers to a disease process derived from multiple causativefactors and characterized by elevated levels of plasma glucose orhyperglycemia in the fasting state or after administration of glucoseduring an oral glucose tolerance test. Persistent or uncontrolledhyperglycemia is associated with increased and premature morbidity andmortality. Often abnormal glucose homeostasis is associated bothdirectly and indirectly with alterations of the lipid, lipoprotein andapolipoprotein metabolism and other metabolic and hemodynamic disease.Therefore patients with Type 2 diabetes mellitus are at especiallyincreased risk of macrovascular and microvascular complications,including coronary heart disease, stroke, peripheral vascular disease,hypertension, nephropathy, neuropathy, and retinopathy. Therefore,therapeutical control of glucose homeostasis, lipid metabolism andhypertension are critically important in the clinical management andtreatment of diabetes mellitus.

There are two generally recognized forms of diabetes. In type 1diabetes, or insulin-dependent diabetes mellitus (IDDM), patientsproduce little or no insulin, the hormone which regulates glucoseutilization. In type 2 diabetes, or noninsulin dependent diabetesmellitus (NIDDM), patients often have plasma insulin levels that are thesame or even elevated compared to nondiabetic subjects; however, thesepatients have developed a resistance to the insulin stimulating effecton glucose and lipid metabolism in the main insulin-sensitive tissues,which are muscle, liver and adipose tissues, and the plasma insulinlevels, while elevated, are insufficient to overcome the pronouncedinsulin resistance.

Insulin resistance is not primarily due to a diminished number ofinsulin receptors but to a post-insulin receptor binding defect that isnot yet understood. This resistance to insulin responsiveness results ininsufficient insulin activation of glucose uptake, oxidation and storagein muscle and inadequate insulin repression of lipolysis in adiposetissue and of glucose production and secretion in the liver.

The available treatments for type 2 diabetes, which have not changedsubstantially in many years, have recognized limitations. While physicalexercise and reductions in dietary intake of calories will dramaticallyimprove the diabetic condition, compliance with this treatment is verypoor because of well-entrenched sedentary lifestyles and excess foodconsumption, especially of foods containing high amounts of saturatedfat. Increasing the plasma level of insulin by administration ofsulfonylureas (e.g. tolbutamide and glipizide) or meglitinide, whichstimulate the pancreatic β-cells to secrete more insulin, and/or byinjection of insulin when sulfonylureas or meglitinide becomeineffective, can result in insulin concentrations high enough tostimulate the very insulin-resistant tissues. However, dangerously lowlevels of plasma glucose can result from administration of insulin orinsulin secretagogues (sulfonylureas or meglitinide), and an increasedlevel of insulin resistance due to the even higher plasma insulin levelscan occur. The biguanides increase insulin sensitivity resulting in somecorrection of hyperglycemia. However, the two biguanides, phenformin andmetformin, can induce lactic acidosis and nausea/diarrhea. Metformin hasfewer side effects than phenformin and is often prescribed for thetreatment of Type 2 diabetes.

The glitazones (i.e. 5-benzylthiazolidine-2,4-diones) are a morerecently described class of compounds with potential for amelioratingmany symptoms of type 2 diabetes. These agents substantially increaseinsulin sensitivity in muscle, liver and adipose tissue in severalanimal models of type 2 diabetes resulting in partial or completecorrection of the elevated plasma levels of glucose without occurrenceof hypoglycemia. The glitazones that are currently marketed are agonistsof the peroxisome proliferator activated receptor (PPAR), primarily thePPAR-gamma subtype. PPAR-gamma agonism is generally believed to beresponsible for the improved insulin sensititization that is observedwith the glitazones. Newer PPAR agonists that are being tested fortreatment of Type II diabetes are agonists of the alpha, gamma or deltasubtype, or a combination of these, and in many cases are chemicallydifferent from the glitazones (i.e., they are not thiazolidinediones).Serious side effects (e.g. liver toxicity) have occurred with some ofthe glitazones, such as troglitazone.

Additional methods of treating the disease are still underinvestigation. New biochemical approaches that have been recentlyintroduced or are still under development include treatment withalpha-glucosidase inhibitors (e.g. acarbose) and protein tyrosinephosphatase-1B (PTP-1B) inhibitors.

Compounds that are inhibitors of the dipeptidyl peptidase-IV (“DP-IV” or“DPP-IV”) enzyme are also under investigation as drugs that may beuseful in the treatment of diabetes, and particularly type 2 diabetes.See for example WO 97/40832, WO 98/19998, U.S. Pat. No. 5,939,560,Bioorg. Med. Chem. Lett., 6(10), 1163-1166 (1996); and Bioorg. Med.Chem. Lett., 6(22), 2745-2748 (1996). The usefulness of DP-IV inhibitorsin the treatment of type 2 diabetes is based on the fact that DP-IV invivo readily inactivates glucagon like peptide-1 (GLP-1) and gastricinhibitory peptide (GIP). GLP-1 and GIP are incretins and are producedwhen food is consumed. The incretins stimulate production of insulin.Inhibition of DP-IV leads to decreased inactivation of the incretins,and this in turn results in increased effectiveness of the incretins instimulating production of insulin by the pancreas. DP-IV inhibitiontherefore results in an increased level of serum insulin.Advantageously, since the incretins are produced by the body only whenfood is consumed, DP-IV inhibition is not expected to increase the levelof insulin at inappropriate times, such as between meals, which can leadto excessively low blood sugar (hypoglycemia). Inhibition of DP-IV istherefore expected to increase insulin without increasing the risk ofhypoglycemia, which is a dangerous side effect associated with the useof insulin secretagogues.

DP-IV inhibitors also have other therapeutic utilities, as discussedherein. DP-IV inhibitors have not been studied extensively to date,especially for utilities other than diabetes. New compounds are neededso that improved DP-IV inhibitors can be found for the treatment ofdiabetes and potentially other diseases and conditions.

SUMMARY OF THE INVENTION

The present invention is directed to compounds which are inhibitors ofthe dipeptidyl peptidase-IV enzyme (“DP-IV inhibitors”) and which areuseful in the treatment or prevention of diseases in which thedipeptidyl peptidase-IV enzyme is involved, such as diabetes andparticularly type 2 diabetes. The invention is also directed topharmaceutical compositions comprising these compounds and the use ofthese compounds and compositions in the prevention or treatment of suchdiseases in which the dipeptidyl peptidase-IV enzyme is involved.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to compounds of the formula I:

wherein:

-   Ar is phenyl which is unsubstituted or substituted with 1-5 of R³,    wherein R³ is independently selected from the group consisting of:    -   (1) halogen,    -   (2) C₁₋₆alkyl, which is linear or branched and is unsubstituted        or substituted with 1-5 halogens,    -   (3) OC₁₋₆alkyl, which is linear or branched and is unsubstituted        or substituted with 1-5 halogens, and    -   (4) CN;-   X is selected from the group consisting of:    -   (1) N, and    -   (2) CR²;        R¹ and R² are independently selected from the group consisting        of:    -   (1) hydrogen,    -   (2) CN,    -   (3) C₁₋₁₀alkyl, which is linear or branched and which is        unsubstituted or substituted with 1-5 halogens or phenyl, which        is unsubstituted or substituted with 1-5 substituents        independently selected from halogen, CN, OH, R⁴, OR⁴, NHSO₂R⁴,        SO₂R⁴, CO₂H, and CO₂C₁₋₆alkyl, wherein the CO₂C₁₋₆alkyl is        linear or branched,    -   (4) phenyl which is unsubstituted or substituted with 1-5        substituents independently selected from halogen, CN, OH, R⁴,        OR⁴, NHSO₂R⁴, SO₂R⁴, CO₂H, and CO₂C₁₋₆alkyl, wherein the        CO₂C₁₋₆alkyl is linear or branched, and    -   (6) a 5- or 6-membered heterocycle which may be saturated or        unsaturated comprising 1-4 heteroatoms independently selected        from N, S and O, the heterocycle being unsubstituted or        substituted with 1-3 substituents independently selected from        oxo, OH, halogen, C₁₋₆alkyl, and OC₁₋₆alkyl, wherein the        C₁₋₆alkyl and OC₁₋₆alkyl are linear or branched and optionally        substituted with 1-5 halogens;-   R⁴ is C₁₋₆alkyl, which is linear or branched and which is    unsubstituted or substituted with 1-5 groups independently selected    from halogen, CO₂H, and CO₂C₁₋₆alkyl, wherein the CO₂C₁₋₆alkyl is    linear or branched;    and pharmaceutically acceptable salts thereof and individual    diastereomers thereof.

An embodiment of the present invention includes compounds of the formulaIa:

wherein X, Ar and R¹ are defined herein;and pharmaceutically acceptable salts and individual diastereomersthereof.

Another embodiment of the present invention includes compounds of theformula Ib:

wherein Ar and R¹ are defined herein;and pharmaceutically acceptable salts and individual diastereomersthereof.

Another embodiment of the present invention includes compounds of theformula Ic:

wherein Ar, R¹ and R² are defined herein;and pharmaceutically acceptable salts thereof and individualdiastereomers thereof.

In the present invention it is preferred that Ar is phenyl which isunsubstituted or substituted with 1-5 substitutents which areindependently selected from the group consisting of:

-   -   (1) fluoro,    -   (2) bromo, and    -   (3) CF₃.

In the present invention it is more preferred that Ar is selected fromthe group consisting of:

-   -   (1) phenyl,    -   (2) 2-fluorophenyl,    -   (3) 3,4-difluorophenyl,    -   (4) 2,5-difluorophenyl,    -   (5) 2,4,5-trifluorophenyl,    -   (6) 2-fluoro-4-(trifluoromethyl)phenyl, and    -   (7) 4-bromo-2,5-difluorophenyl.

In the present invention it is preferred that R¹ is selected from thegroup consisting of:

-   -   (1) hydrogen, and    -   (2) C₁₋₆alkyl, which is linear or branched and which is        unsubstituted or substituted with phenyl or 1-5 fluoro.

In the present invention it is more preferred that R¹ is selected fromthe group consisting of:

-   -   (1) hydrogen,    -   (2) methyl,    -   (3) ethyl,    -   (4) CF₃,    -   (5) CH₂CF₃,    -   (5) CF₂CF₃    -   (6) phenyl, and    -   (7) benzyl.

In the present invention it is more preferred that R¹ is selected fromthe group consisting of:

-   -   (1) hydrogen,    -   (2) methyl,    -   (3) ethyl,    -   (4) CF₃, and    -   (5) CH₂CF₃.

In the present invention it is even more preferred that R¹ is hydrogenor CF₃.

In the present invention it is preferred that R² is selected from:

-   -   (1) hydrogen,    -   (2) C₁₋₆alkyl, which is linear or branched and which is        unsubstituted or substituted with 1-5 fluoro,    -   (3) phenyl, which is unsubstituted or substituted with 1-3        substituents independently selected from fluoro, OCH₃, and OCF₃.

In the present invention it is more preferred that R² is selected fromthe group consisting of:

-   -   (1) hydrogen,    -   (2) methyl,    -   (3) ethyl,    -   (4) CF₃,    -   (5) CH₂CF₃,    -   (5) CF₂CF₃    -   (6) phenyl,    -   (7) (4-methoxy)phenyl,    -   (8) (4-trifluoromethoxy)phenyl,    -   (9) 4-fluorophenyl, and    -   (10) 3,4-difluorophenyl.

In the present invention it is even more preferred that R² is CF₃ orCF₂F₃.

In the present invention it is preferred that R³ is F, Br or CF₃.

The compounds of the present invention may contain one or moreasymmetric centers and can thus occur as racemates and racemic mixtures,single enantiomers, diastereomeric mixtures and individualdiastereomers. The compounds of the instant invention have oneasymmetric center at the beta carbon atom. Additional asymmetric centersmay be present depending upon the nature of the various substituents onthe molecule. Each such asymmetric center will independently produce twooptical isomers and it is intended that all of the possible opticalisomers and diastereomers in mixtures and as pure or partially purifiedcompounds are included within the ambit of this invention. The presentinvention is meant to comprehend all such isomeric forms of thesecompounds.

Some of the compounds described herein contain olefinic double bonds,and unless specified otherwise, are meant to include both E and Zgeometric isomers.

Some of the compounds described herein may exist as tautomers, whichhave different points of attachment of hydrogen accompanied by one ormore double bond shifts. For example, a ketone and its enol form areketo-enol tautomers. The individual tautomers as well as mixturesthereof are encompassed with compounds of the present invention.

Formula I shows the structure of the class of compounds withoutpreferred stereochemistry. Formula Ia shows the preferred sterochemistryat the carbon atom that is attached to the amine group of the beta aminoacid from which these compounds are prepared.

The independent syntheses of these diastereomers or theirchromatographic separations may be achieved as known in the art byappropriate modification of the methodology disclosed herein. Theirabsolute stereochemistry may be determined by the x-ray crystallographyof crystalline products or crystalline intermediates which arederivatized, if necessary, with a reagent containing an asymmetriccenter of known absolute configuration.

If desired, racemic mixtures of the compounds may be separated so thatthe individual enantiomers are isolated. The separation can be carriedout by methods well known in the art, such as the coupling of a racemicmixture of compounds to an enantiomerically pure compound to form adiastereomeric mixture, followed by separation of the individualdiastereomers by standard methods, such as fractional crystallization orchromatography. The coupling reaction is often the formation of saltsusing an enantiomerically pure acid or base. The diasteromericderivatives may then be converted to the pure enantiomers by cleavage ofthe added chiral residue. The racemic mixture of the compounds can alsobe separated directly by chromatographic methods utilizing chiralstationary phases, which methods are well known in the art.

Alternatively, any enantiomer of a compound may be obtained bystereoselective synthesis using optically pure starting materials orreagents of known configuration by methods well known in the art.

The term “pharmaceutically acceptable salts” refers to salts preparedfrom pharmaceutically acceptable non-toxic bases or acids includinginorganic or organic bases and inorganic or organic acids. Salts derivedfrom inorganic bases include aluminum, ammonium, calcium, copper,ferric, ferrous, lithium, magnesium, manganic salts, manganous,potassium, sodium, zinc, and the like. Particularly preferred are theammonium, calcium, magnesium, potassium, and sodium salts. Salts in thesolid form may exist in more than one crystal structure, and may also bein the form of hydrates. Salts derived from pharmaceutically acceptableorganic non-toxic bases include salts of primary, secondary, andtertiary amines, substituted amines including naturally occurringsubstituted amines, cyclic amines, and basic ion exchange resins, suchas arginine, betaine, caffeine, choline, N,N′-dibenzylethylenediamine,diethylamine, 2-diethylaminoethanol, 2-dimethylaminoethanol,ethanolamine, ethylenediamine, N-ethyl-morpholine, N-ethylpiperidine,glucamine, glucosamine, histidine, hydrabamine, isopropylamine, lysine,methylglucamine, morpholine, piperazine, piperidine, polyamine resins,procaine, purines, theobromine, triethylamine, trimethylamine,tripropylamine, tromethamine, and the like.

When the compound of the present invention is basic, salts may beprepared from pharmaceutically acceptable non-toxic acids, includinginorganic and organic acids. Such acids include acetic, benzenesulfonic,benzoic, camphorsulfonic, citric, ethanesulfonic, fumaric, gluconic,glutamic, hydrobromic, hydrochloric, isethionic, lactic, maleic, malic,mandelic, methanesulfonic, mucic, nitric, pamoic, pantothenic,phosphoric, succinic, sulfuric, tartaric, p-toluenesulfonic acid, andthe like. Particularly preferred are citric, hydrobromic, hydrochloric,maleic, phosphoric, sulfuric, fumaric, and tartaric acids.

It will be understood that, as used herein, references to the compoundsof Formula I are meant to also include the pharmaceutically acceptablesalts.

As appreciated by those of skill in the art, halo or halogen as usedherein are intended to include fluoro, chloro, bromo and iodo.Similarly, C₁₋₈, as in C₁₋₈alkyl is defined to identify the group ashaving 1, 2, 3, 4, 5, 6, 7 or 8 carbons in a linear or branchedarrangement, such that C₁₋₈alkyl specifically includes methyl, ethyl,n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, pentyl, hexyl,heptyl and octyl. Likewise, C₀, as in C₀alkyl is defined to identify thepresence of a direct covalent bond. A group which is designated as beingindependently substituted with substituents may be independentlysubstituted with multiple numbers of such substituents. The term“heterocycle” as used herein is intended to include 5- or 6-memberedring systems which are within the following listing: benzimidazolyl,benzodioxanyl, benzofuranyl, benzopyrazolyl, benzothiadiazolyl,benzotriazolyl, benzothiophenyl, benzoxadiazolyl, benzoxazolyl,carbazolyl, carbolinyl, chromanyl, cinnolinyl, furanyl, imidazolyl,indolinyl, indolyl, indolazinyl, indazolyl, isobenzofuranyl, isoindolyl,isoquinolyl, isothiazolyl, isoxazolyl, naphthyridinyl, oxadiazolyl,oxazolyl, pyrazinyl, pyrazolyl, pyridopyridinyl, pyridazinyl, pyridyl,pyrimidyl, pyrrolyl, quinazolinyl, quinolinyl, quinoxalinyl, tetrazolyl,thiadiazolyl, thiazolidinyl, thiazolyl, thienyl, triazolyl, azetidinyl,1,4-dioxanyl, hexahydroazepinyl, piperazinyl, piperidinyl, pyrrolidinyl,morpholinyl, thiomorpholinyl, dihydrobenzimidazolyl,dihydrobenzofuranyl, dihydrobenzothiophenyl, dihydrobenzoxazolyl,dihydrofuranyl, dihydroimidazolyl, dihydroindolyl, dihydroisooxazolyl,dihydroisothiazolyl, dihydrooxadiazolyl, dihydrooxazolyl,dihydropyrazinyl, dihydropyrazolyl, dihydropyridinyl,dihydropyrimidinyl, dihydropyrrolyl, dihydroquinolinyl,dihydrotetrazolyl, dihydrothiadiazolyl, dihydrothiazolyl,dihydrothienyl, dihydrotriazolyl, dihydroazetidinyl,methylenedioxybenzoyl, tetrahydrofuranyl, tetrahydroimidazolyl,tetrahydroisoquinolinyl, and tetrahydrothienyl.

Exemplifying the invention is the use of the compounds disclosed in theExamples and herein.

Specific compounds within the present invention include a compound whichselected from the group consisting of the compounds disclosed in thefollowing Examples and pharmaceutically acceptable salts thereof andindividual diastereomers thereof.

The subject compounds are useful in a method of inhibiting thedipeptidyl peptidase-IV enzyme in a patient such as a mammal in need ofsuch inhibition comprising the administration of an effective amount ofthe compound. The present invention is directed to the use of thecompounds disclosed herein as inhibitors of dipeptidyl peptidase-IVenzyme activity.

In addition to primates, such as humans, a variety of other mammals canbe treated according to the method of the present invention. Forinstance, mammals including, but not limited to, cows, sheep, goats,horses, dogs, cats, guinea pigs, rats or other bovine, ovine, equine,canine, feline, rodent or murine species can be treated. However, themethod can also be practiced in other species, such as avian species(e.g., chickens).

The present invention is further directed to a method for themanufacture of a medicament for inhibiting dipeptidyl peptidase-IVenzyme activity in humans and animals comprising combining a compound ofthe present invention with a pharmaceutical carrier or diluent.

The subject treated in the present methods is generally a mammal,preferably a human being, male or female, in whom inhibition ofdipeptidyl peptidase-IV enzyme activity is desired. The term“therapeutically effective amount” means the amount of the subjectcompound that will elicit the biological or medical response of atissue, system, animal or human that is being sought by the researcher,veterinarian, medical doctor or other clinician.

The term “composition” as used herein is intended to encompass a productcomprising the specified ingredients in the specified amounts, as wellas any product which results, directly or indirectly, from combinationof the specified ingredients in the specified amounts. Such term inrelation to pharmaceutical composition, is intended to encompass aproduct comprising the active ingredient(s), and the inert ingredient(s)that make up the carrier, as well as any product which results, directlyor indirectly, from combination, complexation or aggregation of any twoor more of the ingredients, or from dissociation of one or more of theingredients, or from other types of reactions or interactions of one ormore of the ingredients. Accordingly, the pharmaceutical compositions ofthe present invention encompass any composition made by admixing acompound of the present invention and a pharmaceutically acceptablecarrier. By “pharmaceutically acceptable” it is meant the carrier,diluent or excipient must be compatible with the other ingredients ofthe formulation and not deleterious to the recipient thereof.

The terms “administration of” and or “administering a” compound shouldbe understood to mean providing a compound of the invention or a prodrugof a compound of the invention to the individual in need of treatment.

The utility of the compounds in accordance with the present invention asinhibitors of dipeptidyl peptidase-IV enzyme activity may bedemonstrated by methodology known in the art. Inhibition constants aredetermined as follows. A continuous fluorometric assay is employed withthe substrate Gly-Pro-AMC, which is cleaved by DP-IV to release thefluorescent AMC leaving group. The kinetic parameters that describe thisreaction are as follows: K_(m)=50 μM; k_(cat)=75 s⁻¹;k_(cat)/K_(m)=1.5×10⁶ M⁻¹s⁻¹. A typical reaction contains approximately50 pM enzyme, 50 μM Gly-Pro-AMC, and buffer (100 mM HEPES, pH 7.5, 0.1mg/ml BSA) in a total reaction volume of 100 μl. Liberation of AMC ismonitored continuously in a 96-well plate fluorometer using anexcitation wavelength of 360 nm and an emission wavelength of 460 nm.Under these conditions, approximately 0.8 μM AMC is produced in 30minutes at 25 degrees C. The enzyme used in these studies was soluble(transmembrane domain and cytoplasmic extension excluded) human proteinproduced in a baculovirus expression system (Bac-To-Bac, Gibco BRL). Thekinetic constants for hydrolysis of Gly-Pro-AMC and GLP-1 were found tobe in accord with literature values for the native enzyme. To measurethe dissociation constants for compounds, solutions of inhibitor in DMSOwere added to reactions containing enzyme and substrate (final DMSOconcentration is 1%). All experiments were conducted at room temperatureusing the standard reaction conditions described above. To determine thedissociation constants (K_(i)), reaction rates were fit by non-linearregression to the Michaelis-Menton equation for competitive inhibition.The errors in reproducing the dissociation constants are typically lessthan two-fold.

In particular, the compounds of the following examples had activity ininhibiting the dipeptidyl peptidase-IV enzyme in the aforementionedassays, generally with an IC₅₀ of less than about 1 μM. Such a result isindicative of the intrinsic activity of the compounds in use asinhibitors the dipeptidyl peptidase-IV enzyme activity.

Dipeptidyl peptidase-IV enzyme (DP-IV) is a cell surface protein thathas been implicated in a wide range of biological functions. It has abroad tissue distribution (intestine, kidney, liver, pancreas, placenta,thymus, spleen, epithelial cells, vascular endothelium, lymphoid andmyeloid cells, serum), and distinct tissue and cell-type expressionlevels. DP-IV is identical to the T cell activation marker CD26, and itcan cleave a number of immunoregulatory, endocrine, and neurologicalpeptides in vitro. This has suggested a potential role for thispeptidase in a variety of disease processes in humans or other species.

Accordingly, the subject compounds are useful in a method for theprevention or treatment of the following diseases, disorders andconditions.

Type II Diabetes and Related Disorders:

It is well established that the incretins GLP-1 and GIP are rapidlyinactivated in vivo by DP-IV. Studies with DP-IV^((−/−))-deficient miceand preliminary clinical trials indicate that DP-IV inhibition increasesthe steady state concentrations of GLP-1 and GIP, resulting in improvedglucose tolerance. By analogy to GLP-1 and GIP, it is likely that otherglucagon family peptides involved in glucose regulation are alsoinactivated by DP-IV (eg. PACAP, glucagon). Inactivation of thesepeptides by DP-IV may also play a role in glucose homeostasis.

The DP-IV inhibitors of the present invention therefore have utility inthe treatment of type II diabetes and in the treatment and prevention ofthe numerous conditions that often accompany Type II diabetes, includingmetabolic syndrome X, reactive hypoglycemia, and diabetic dyslipidemia.Obesity, discussed below, is another condition that is often found withType II diabetes that may respond to treatment with the compounds ofthis invention.

The following diseases, disorders and conditions are related to Type 2diabetes, and therefore may be treated, controlled or in some casesprevented, by treatment with the compounds of this invention: (1)hyperglycemia, (2) low glucose tolerance, (3) insulin resistance, (4)obesity, (5) lipid disorders, (6) dyslipidemia, (7) hyperlipidemia, (8)hypertriglyceridemia, (9) hypercholesterolemia, (10) low HDL levels,(11) high LDL levels, (12) atherosclerosis and its sequelae, (13)vascular restenosis, (14) irritable bowel syndrome, (15) inflammatorybowel disease, including Crohn's disease and ulcerative colitis, (16)other inflammatory conditions, (17) pancreatitis, (18) abdominalobesity, (19) neurodegenerative disease, (20) retinopathy, (21)nephropathy, (22) neuropathy, (23) Syndrome X, (24) ovarianhyperandrogenism (polycystic ovarian syndrome), and other disorderswhere insulin resistance is a component.

Obesity:

DP-IV inhibitors may be useful for the treatment of obesity. This isbased on the observed inhibitory effects on food intake and gastricemptying of GLP-1 and GLP-2. Exogenous administration of GLP-1 in humanssignificantly decreases food intake and slows gastric emptying (Am. J.Physiol. 277, R910-R916 (1999)). ICV administration of GLP-1 in rats andmice also has profound effects on food intake (Nature Medicine 2,1254-1258 (1996)). This inhibition of feeding is not observed inGLP-1R^((−/−)) mice, indicating that these effects are mediated throughbrain GLP-1 receptors. By analogy to GLP-1, it is likely that GLP-2 isalso regulated by DP-IV. ICV administration of GLP-2 also inhibits foodintake, analogous to the effects observed with GLP-1 (Nature Medicine 6,802-807 (2000)).

Growth Hormone Deficiency:

DP-IV inhibition may be useful for the treatment of growth hormonedeficiency, based on the hypothesis that growth-hormone releasing factor(GRF), a peptide that stimulates release of growth hormone from theanterior pituitary, is cleaved by the DP-IV enzyme in vivo (WO00/56297). The following data provide evidence that GRF is an endogenoussubstrate: (1) GRF is efficiently cleaved in vitro to generate theinactive product GRF[3-44] (BBA 1122, 147-153 (1992)); (2) GRF israpidly degraded in plasma to GRF[3-44]; this is prevented by the DP-IVinhibitor diprotin A; and (3) GRF[3-44] is found in the plasma of ahuman GRF transgenic pig (J. Clin. Invest. 83, 1533-1540 (1989)). ThusDP-IV inhibitors may be useful for the same spectrum of indicationswhich have been considered for growth hormone secretagogues.

Intestinal Injury:

The potential for using DP-IV inhibitors for the treatment of intestinalinjury is suggested by the results of studies indicating thatglucagon-like peptide-2 (GLP-2), a likely endogenous substrate forDP-IV, may exhibit trophic effects on the intestinal epithelium(Regulatory Peptides 90, 27-32 (2000)). Administration of GLP-2 resultsin increased small bowel mass in rodents and attenuates intestinalinjury in rodent models of colitis and enteritis.

Immunosuppression:

DP-IV inhibition may be useful for modulation of the immune response,based upon studies implicating the DP-IV enzyme in T cell activation andin chemokine processing, and efficacy of DP-IV inhibitors in in vivomodels of disease. DP-IV has been shown to be identical to CD26, a cellsurface marker for activated immune cells. The expression of CD26 isregulated by the differentiation and activation status of immune cells.It is generally accepted that CD26 functions as a co-stimulatorymolecule in in vitro models of T cell activation. A number of chemokinescontain proline in the penultimate position, presumably to protect themfrom degradation by non-specific aminopeptidases. Many of these havebeen shown to be processed in vitro by DP-IV. In several cases (RANTES,LD78-beta, MDC, eotaxin, SDF-1alpha), cleavage results in an alteredactivity in chemotaxis and signaling assays. Receptor selectivity alsoappears to be modified in some cases (RANTES). Multiple N-terminallytruncated forms of a number of chemokines have been identified in invitro cell culture systems, including the predicted products of DP-IVhydrolysis.

DP-IV inhibitors have been shown to be efficacious immunosupressants inanimal models of transplantation and arthritis. Prodipine(Pro-Pro-diphenyl-phosphonate), an irreversible inhibitor of DP-IV, wasshown to double cardiac allograft survival in rats from day 7 to day 14(Transplantation 63, 1495-1500 (1997)). DP-IV inhibitors have beentested in collagen and alkyldiamine-induced arthritis in rats and showeda statistically significant attenuation of hind paw swelling in thismodel (Int J Immunopharmacology 19, 15-24 (1997), Immunopharmacology 40,21-26 (1998)). DP-IV is upregulated in a number of autoimmune diseasesincluding rheumatoid arthritis, multiple sclerosis, Graves' disease, andHashimoto's thyroiditis (Immunology Today 20, 367-375 (1999)).

HIV Infection:

DP-IV inhibition may be useful for the treatment or prevention of HIVinfection or AIDS because a number of chemokines which inhibit HIV cellentry are potential substrates for DP-IV (Immunology Today 20, 367-375(1999)). In the case of SDF-1alpha, cleavage decreases antiviralactivity (PNAS 95, 6331-6 (1998)). Thus, stabilization of SDF-1alphathrough inhibition of DP-IV would be expected to decrease HIVinfectivity.

Hematopoiesis:

DP-IV inhibition may be useful for the treatment or prevention ofhematopiesis because DP-IV may be involved in hematopoiesis. A DP-IVinhibitor, Val-Boro-Pro, stimulated hematopoiesis in a mouse model ofcyclophosphamide-induced neutropenia (WO 99/56753).

Neuronal Disorders:

DP-IV inhibition may be useful for the treatment or prevention ofvarious neuronal or psychiatric disorders because a number of peptidesimplicated in a variety of neuronal processes are cleaved in vitro byDP-IV. A DP-IV inhibitor thus may have a therapeutic benefit in thetreatment of neuronal disorders. Endomorphin-2, beta-casomorphin, andsubstance P have all been shown to be in vitro substrates for DP-IV. Inall cases, in vitro cleavage is highly efficient, with k_(cat)/K_(m)˜10⁶M⁻¹s⁻¹ or greater. In an electric shock jump test model of analgesia inrats, a DP-IV inhibitor showed a significant effect that was independentof the presence of exogenous endomorphin-2 (Brain Research 815, 278-286(1999)).

Tumor Invasion and Metastasis:

DP-IV inhibition may be useful for the treatment or prevention of tumorinvasion and metastasis because an increase or decrease in expression ofseveral ectopeptidases including DP-IV has been observed during thetransformation of normal cells to a malignant phenotype (J. Exp. Med.190, 301-305 (1999)). Up- or down-regulation of these proteins appearsto be tissue and cell-type specific. For example, increased CD26/DP-IVexpression has been observed on T cell lymphoma, T cell acutelymphoblastic leukemia, cell-derived thyroid carcinomas, basal cellcarcinomas, and breast carcinomas. Thus, DP-IV inhibitors may haveutility in the treatment of such carcinomas.

Benign Prostatic Hypertrophy:

DP-IV inhibition may be useful for the treatment of benign prostatichypertrophy because increased DP-IV activity was noted in prostatetissue from patients with BPH (Eur. J. Clin. Chem. Clin. Biochem 30,333-338 (1992)).

Sperm Motility/Male Contraception:

DP-IV inhibition may be useful for the altering sperm motility and formale contraception because in seminal fluid, prostatosomes, prostatederived organelles important for sperm motility, possess very highlevels of DP-IV activity (Eur. J. Clin. Chem. Clin. Biochem 30, 333-338(1992)).

Gingivitis:

DP-IV inhibition may be useful for the treatment of gingivitis becauseDP-IV activity was found in gingival crevicular fluid and in somestudies correlated with periodontal disease severity (Arch. Oral Biol.37, 167-173 (1992)).

Osteoporosis:

DP-IV inhibition may be useful for the treatment or prevention ofosteoporosis because GIP receptors are present in osteoblasts.

The compounds of the present invention have utility in treating orpreventing one or more of the following conditions or diseases: (1)hyperglycemia, (2) low glucose tolerance, (3) insulin resistance, (4)obesity, (5) lipid disorders, (6) dyslipidemia, (7) hyperlipidemia, (8)hypertriglyceridemia, (9) hypercholesterolemia, (10) low HDL levels,(11) high LDL levels, (12) atherosclerosis and its sequelae, (13)vascular restenosis, (14) irritable bowel syndrome, (15) inflammatorybowel disease, including Crohn's disease and ulcerative colitis, (16)other inflammatory conditions, (17) pancreatitis, (18) abdominalobesity, (19) neurodegenerative disease, (20) retinopathy, (21)nephropathy, (22) neuropathy, (23) Syndrome X, (24) ovarianhyperandrogenism (polycystic ovarian syndrome), (25) Type II diabetes,(26) growth hormone deficiency, (27) neutropenia, (28) neuronaldisorders, (29) tumor metastasis, (30) benign prostatic hypertrophy,(32) gingivitis, (33) hypertension, (34) osteoporosis, and otherconditions that may be treated or prevented by inhibition of DP-IV.

The subject compounds are further useful in a method for the preventionor treatment of the aforementioned diseases, disorders and conditions incombination with other agents.

The compounds of the present invention may be used in combination withone or more other drugs in the treatment, prevention, suppression oramelioration of diseases or conditions for which compounds of Formula Ior the other drugs may have utility, where the combination of the drugstogether are safer or more effective than either drug alone. Such otherdrug(s) may be administered, by a route and in an amount commonly usedtherefor, contemporaneously or sequentially with a compound of FormulaI. When a compound of Formula I is used contemporaneously with one ormore other drugs, a pharmaceutical composition in unit dosage formcontaining such other drugs and the compound of Formula I is preferred.However, the combination therapy may also includes therapies in whichthe compound of Formula I and one or more other drugs are administeredon different overlapping schedules. It is also contemplated that whenused in combination with one or more other active ingredients, thecompounds of the present invention and the other active ingredients maybe used in lower doses than when each is used singly. Accordingly, thepharmaceutical compositions of the present invention include those thatcontain one or more other active ingredients, in addition to a compoundof Formula I.

Examples of other active ingredients that may be administered incombination with a compound of Formula I, and either administeredseparately or in the same pharmaceutical composition, include, but arenot limited to:

(a) other dipeptidyl peptidase IV (DP-IV) inhibitors;

(b) insulin sensitizers including (i) PPARγ agonists such as theglitazones (e.g. troglitazone, pioglitazone, englitazone, MCC-555,rosiglitazone, and the like) and other PPAR ligands, including PPARα/γdual agonists, such as KRP-297, and PPARα agonists such as fenofibricacid derivatives (gemfibrozil, clofibrate, fenofibrate and bezafibrate),(ii) biguanides such as metformin and phenformin, and (iii) proteintyrosine phosphatase-1B (PTP-1B) inhibitors;

(c) insulin or insulin mimetics;

(d) sulfonylureas and other insulin secretagogues such as tolbutamideand glipizide, meglitinide, and related materials;

(e) α-glucosidase inhibitors (such as acarbose);

(f) glucagon receptor antagonists such as those disclosed in WO98/04528, WO 99/01423, WO 00/39088, and WO 00/69810;

(g) GLP-1, GLP-1 mimetics, and GLP-1 receptor agonists such as thosedisclosed in WO00/42026 and WO00/59887;

(h) GIP and GIP mimetics such as those disclosed in WO00/58360, and GIPreceptor agonists;

(i) PACAP, PACAP mimetics, and PACAP receptor δ agonists such as thosedisclosed in WO 01/23420;

(j) cholesterol lowering agents such as (i) HMG-CoA reductase inhibitors(lovastatin, simvastatin, pravastatin, fluvastatin, atorvastatin,rivastatin, itavastatin, rosuvastatin, and other statins), (ii)sequestrants (cholestyramine, colestipol, and dialkylaminoalkylderivatives of a cross-linked dextran), (iii) nicotinyl alcohol,nicotinic acid or a salt thereof, (iv) PPARα agonists such as fenofibricacid derivatives (gemfibrozil, clofibrate, fenofibrate and bezafibrate),(v) PPARα/γ dual agonists, such as KRP-297, (vi) inhibitors ofcholesterol absorption, such as beta-sitosterol and ezetimibe, (vii)acyl CoA:cholesterol acyltransferase inhibitors, such as avasimibe, and(viii) anti-oxidants, such as probucol;

(k) PPAR agonists, such as those disclosed in WO97/28149;

(l) antiobesity compounds such as fenfluramine, dexfenfluramine,phentermine, sibutramine, orlistat, neuropeptide Y5 inhibitors, and β3adrenergic receptor agonists;

(m) an ileal bile acid transporter inhibitor; and

(n) agents intended for use in inflammatory conditions such as aspirin,non-steroidal anti-inflammatory drugs, glucocorticoids, azulfidine, andcyclo-oxygenase 2 selective inhibitors.

The above combinations include combinations of a compound of the presentinvention not only with one other active compound, but also with two ormore other active compounds. Non-limiting examples include combinationsof compounds having Formula I with two or more active compounds selectedfrom biguanides, sulfonylureas, HMG-CoA reductase inhibitors, PPARagonists, PTP-1B inhibitors, other DP-IV inhibitors, and anti-obesitycompounds.

Likewise, compounds of the present invention may be used in combinationwith other drugs that are used in the treatment/prevention/suppressionor amelioration of the diseases or conditions for which compounds of thepresent invention are useful. Such other drugs may be administered, by aroute and in an amount commonly used therefor, contemporaneously orsequentially with a compound of the present invention. When a compoundof the present invention is used contemporaneously with one or moreother drugs, a pharmaceutical composition containing such other drugs inaddition to the compound of the present invention is preferred.Accordingly, the pharmaceutical compositions of the present inventioninclude those that also contain one or more other active ingredients, inaddition to a compound of the present invention.

The weight ratio of the compound of the compound of the presentinvention to the second active ingredient may be varied and will dependupon the effective dose of each ingredient. Generally, an effective doseof each will be used. Thus, for example, when a compound of the presentinvention is combined with another agent, the weight ratio of thecompound of the present invention to the other agent will generallyrange from about 1000:1 to about 1:1000, preferably about 200:1 to about1:200. Combinations of a compound of the present invention and otheractive ingredients will generally also be within the aforementionedrange, but in each case, an effective dose of each active ingredientshould be used.

In such combinations the compound of the present invention and otheractive agents may be administered separately or in conjunction. Inaddition, the administration of one element may be prior to, concurrentto, or subsequent to the administration of other agent(s).

The compounds of the present invention may be administered by oral,parenteral (e.g., intramuscular, intraperitoneal, intravenous, ICV,intracisternal injection or infusion, subcutaneous injection, orimplant), by inhalation spray, nasal, vaginal, rectal, sublingual, ortopical routes of administration and may be formulated, alone ortogether, in suitable dosage unit formulations containing conventionalnon-toxic pharmaceutically acceptable carriers, adjuvants and vehiclesappropriate for each route of administration. In addition to thetreatment of warm-blooded animals such as mice, rats, horses, cattle,sheep, dogs, cats, monkeys, etc., the compounds of the invention areeffective for use in humans.

The pharmaceutical compositions for the administration of the compoundsof this invention may conveniently be presented in dosage unit form andmay be prepared by any of the methods well known in the art of pharmacy.All methods include the step of bringing the active ingredient intoassociation with the carrier which constitutes one or more accessoryingredients. In general, the pharmaceutical compositions are prepared byuniformly and intimately bringing the active ingredient into associationwith a liquid carrier or a finely divided solid carrier or both, andthen, if necessary, shaping the product into the desired formulation. Inthe pharmaceutical composition the active object compound is included inan amount sufficient to produce the desired effect upon the process orcondition of diseases. As used herein, the term “composition” isintended to encompass a product comprising the specified ingredients inthe specified amounts, as well as any product which results, directly orindirectly, from combination of the specified ingredients in thespecified amounts.

The pharmaceutical compositions containing the active ingredient may bein a form suitable for oral use, for example, as tablets, troches,lozenges, aqueous or oily suspensions, dispersible powders or granules,emulsions, hard or soft capsules, or syrups or elixirs. Compositionsintended for oral use may be prepared according to any method known tothe art for the manufacture of pharmaceutical compositions and suchcompositions may contain one or more agents selected from the groupconsisting of sweetening agents, flavoring agents, coloring agents andpreserving agents in order to provide pharmaceutically elegant andpalatable preparations. Tablets contain the active ingredient inadmixture with non-toxic pharmaceutically acceptable excipients whichare suitable for the manufacture of tablets. These excipients may be forexample, inert diluents, such as calcium carbonate, sodium carbonate,lactose, calcium phosphate or sodium phosphate; granulating anddisintegrating agents, for example, corn starch, or alginic acid;binding agents, for example starch, gelatin or acacia, and lubricatingagents, for example magnesium stearate, stearic acid or talc. Thetablets may be uncoated or they may be coated by known techniques todelay disintegration and absorption in the gastrointestinal tract andthereby provide a sustained action over a longer period. For example, atime delay material such as glyceryl monostearate or glyceryl distearatemay be employed. They may also be coated by the techniques described inthe U.S. Pat. Nos. 4,256,108; 4,166,452; and 4,265,874 to form osmotictherapeutic tablets for control release.

Formulations for oral use may also be presented as hard gelatin capsuleswherein the active ingredient is mixed with an inert solid diluent, forexample, calcium carbonate, calcium phosphate or kaolin, or as softgelatin capsules wherein the active ingredient is mixed with water or anoil medium, for example peanut oil, liquid paraffin, or olive oil.

Aqueous suspensions contain the active materials in admixture withexcipients suitable for the manufacture of aqueous suspensions. Suchexcipients are suspending agents, for example sodiumcarboxymethylcellulose, methylcellulose, hydroxy-propylmethylcellulose,sodium alginate, polyvinyl-pyrrolidone, gum tragacanth and gum acacia;dispersing or wetting agents may be a naturally-occurring phosphatide,for example lecithin, or condensation products of an alkylene oxide withfatty acids, for example polyoxyethylene stearate, or condensationproducts of ethylene oxide with long chain aliphatic alcohols, forexample heptadecaethyleneoxycetanol, or condensation products ofethylene oxide with partial esters derived from fatty acids and ahexitol such as polyoxyethylene sorbitol monooleate, or condensationproducts of ethylene oxide with partial esters derived from fatty acidsand hexitol anhydrides, for example polyethylene sorbitan monooleate.The aqueous suspensions may also contain one or more preservatives, forexample ethyl, or n-propyl, p-hydroxybenzoate, one or more coloringagents, one or more flavoring agents, and one or more sweetening agents,such as sucrose or saccharin.

Oily suspensions may be formulated by suspending the active ingredientin a vegetable oil, for example arachis oil, olive oil, sesame oil orcoconut oil, or in a mineral oil such as liquid paraffin. The oilysuspensions may contain a thickening agent, for example beeswax, hardparaffin or cetyl alcohol. Sweetening agents such as those set forthabove, and flavoring agents may be added to provide a palatable oralpreparation. These compositions may be preserved by the addition of ananti-oxidant such as ascorbic acid.

Dispersible powders and granules suitable for preparation of an aqueoussuspension by the addition of water provide the active ingredient inadmixture with a dispersing or wetting agent, suspending agent and oneor more preservatives. Suitable dispersing or wetting agents andsuspending agents are exemplified by those already mentioned above.Additional excipients, for example sweetening, flavoring and coloringagents, may also be present.

The pharmaceutical compositions of the invention may also be in the formof oil-in-water emulsions. The oily phase may be a vegetable oil, forexample olive oil or arachis oil, or a mineral oil, for example liquidparaffin or mixtures of these. Suitable emulsifying agents may benaturally-occurring gums, for example gum acacia or gum tragacanth,naturally-occurring phosphatides, for example soy bean, lecithin, andesters or partial esters derived from fatty acids and hexitolanhydrides, for example sorbitan monooleate, and condensation productsof the said partial esters with ethylene oxide, for examplepolyoxyethylene sorbitan monooleate. The emulsions may also containsweetening and flavoring agents.

Syrups and elixirs may be formulated with sweetening agents, for exampleglycerol, propylene glycol, sorbitol or sucrose. Such formulations mayalso contain a demulcent, a preservative and flavoring and coloringagents.

The pharmaceutical compositions may be in the form of a sterileinjectable aqueous or oleagenous suspension. This suspension may beformulated according to the known art using those suitable dispersing orwetting agents and suspending agents which have been mentioned above.The sterile injectable preparation may also be a sterile injectablesolution or suspension in a non-toxic parenterally-acceptable diluent orsolvent, for example as a solution in 1,3-butane diol. Among theacceptable vehicles and solvents that may be employed are water,Ringer's solution and isotonic sodium chloride solution. In addition,sterile, fixed oils are conventionally employed as a solvent orsuspending medium. For this purpose any bland fixed oil may be employedincluding synthetic mono- or diglycerides. In addition, fatty acids suchas oleic acid find use in the preparation of injectables.

The compounds of the present invention may also be administered in theform of suppositories for rectal administration of the drug. Thesecompositions can be prepared by mixing the drug with a suitablenon-irritating excipient which is solid at ordinary temperatures butliquid at the rectal temperature and will therefore melt in the rectumto release the drug. Such materials are cocoa butter and polyethyleneglycols.

For topical use, creams, ointments, jellies, solutions or suspensions,etc., containing the compounds of The present invention are employed.(For purposes of this application, topical application shall includemouth washes and gargles.)

The pharmaceutical composition and method of the present invention mayfurther comprise other therapeutically active compounds as noted hereinwhich are usually applied in the treatment of the above mentionedpathological conditions.

In the treatment or prevention of conditions which require inhibition ofdipeptidyl peptidase-IV enzyme activity an appropriate dosage level willgenerally be about 0.01 to 500 mg per kg patient body weight per daywhich can be administered in single or multiple doses. Preferably, thedosage level will be about 0.1 to about 250 mg/kg per day; morepreferably about 0.5 to about 100 mg/kg per day. A suitable dosage levelmay be about 0.01 to 250 mg/kg per day, about 0.05 to 100 mg/kg per day,or about 0.1 to 50 mg/kg per day. Within this range the dosage may be0.05 to 0.5, 0.5 to 5 or 5 to 50 mg/kg per day. For oral administration,the compositions are preferably provided in the form of tabletscontaining 1.0 to 1000 milligrams of the active ingredient, particularly1.0, 5.0, 10.0, 15.0, 20.0, 25.0, 50.0, 75.0, 100.0, 150.0, 200.0,250.0, 300.0, 400.0, 500.0, 600.0, 750.0, 800.0, 900.0, and 1000.0milligrams of the active ingredient for the symptomatic adjustment ofthe dosage to the patient to be treated. The compounds may beadministered on a regimen of 1 to 4 times per day, preferably once ortwice per day.

When treating or preventing diabetes mellitus and/or hyperglycemia orhypertriglyceridemia or other diseases for which compounds of thepresent invention are indicated, generally satisfactory results areobtained when the compounds of the present invention are administered ata daily dosage of from about 0.1 milligram to about 100 milligram perkilogram of animal body weight, preferably given as a single daily doseor in divided doses two to six times a day, or in sustained releaseform. For most large mammals, the total daily dosage is from about 1.0milligrams to about 1000 milligrams, preferably from about 1 milligramsto about 50 milligrams. In the case of a 70 kg adult human, the totaldaily dose will generally be from about 7 milligrams to about 350milligrams. This dosage regimen may be adjusted to provide the optimaltherapeutic response.

It will be understood, however, that the specific dose level andfrequency of dosage for any particular patient may be varied and willdepend upon a variety of factors including the activity of the specificcompound employed, the metabolic stability and length of action of thatcompound, the age, body weight, general health, sex, diet, mode and timeof administration, rate of excretion, drug combination, the severity ofthe particular condition, and the host undergoing therapy.

Several methods for preparing the compounds of this invention areillustrated in the following Schemes and Examples. Starting materialsare made according to procedures known in the art or as illustratedherein.

The compounds of the present invention can be prepared from beta aminoacid intermediates such as those of formula II and substitutedheterocyclic intermediates such as those of formula III, using standardpeptide coupling conditions followed by deprotection. The preparation ofthese intermediates is described in the following schemes.

where Ar, X and R¹ are as defined above and P is a suitable nitrogenprotecting group such as tert-butoxycarbonyl, benzyloxycarbonyl, or9-fluorenylmethoxycarbonyl.

Compounds of formula II are commercially available, known in theliterature or may be conveniently prepared by a variety of methodsfamiliar to those skilled in the art. One common route is illustrated inScheme 1. Acid 1, which may be commercially available or readilyprepared from the corresponding amino acid by protection using, forexample, di-tert-butyl-dicarbonate (for P=Boc), carbobenzyloxy chloride(for P=Cbz), or N-(9-fluorenylmethoxycarbonyloxy)succinimide (forP=Fmoc), is treated with isobutyl chloroformate and a base such astriethylamine or diisopropylethylamine, followed by diazomethane. Theresultant diazoketone is then treated with silver benzoate in a solventsuch as methanol or aqueous dioxane and may be subjected to sonicationfollowing the procedure of Sewald et al., Synthesis, 837 (1997) in orderto provide the beta amino acid II. As will be understood by thoseskilled in the art, for the preparation of enantiomerically pure betaamino acids II, enantiomerically pure alpha amino acids 1 may be used.Alternate routes to these compounds can be found in the followingreviews: E. Juaristi, Enantioselective Synthesis of β-Amino Acids, Ed.,Wiley-VCH, New York: 1997, Juaristi et al., Aldrichimica Acta, 27, 3(1994), Cole et al., Tetrahedron, 32, 9517 (1994).

Compounds III are commercially available, known in the literature or maybe conveniently prepared by a variety of methods familiar to thoseskilled in the art. One convenient method is shown in Scheme 2.Unsaturated derivative 2 is reduced, for example, by treatment withhydrogen gas and a catalyst such as palladium on carbon or platinumoxide in a solvent such as methanol or ethanol to provide Compound III.

Intermediates 2, from Scheme 2, are themselves commercially available,known in the literature or may be conveniently prepared by a variety ofmethods familiar to those skilled in the art. One such method when X isCR² is illustrated in Scheme 3. Aminopyrazine 3 is treated with a2-haloketone such as 2-bromoketone 4 in a solvent such as methanol orethanol to provide intermediate 2a. Alternatively, for the preparationof intermediate 2a where R² is H, 2-bromo-dimethylacetal 5 and acatalytic amount of acid such as hydrochloric acid may be employedinstead of intermediate 4.

A convenient method for the preparation of intermediate 2b, where X isN, is illustrated in Scheme 4. Chloropyrazine 6 is treated withhydrazine to provide hydrazinopyrazine 7. Compound 7 may be condensedwith either an orthoester such as triethyl orthoester 8 to give 2b orwith a carboxylic acid 9 in polyphosphoric acid at elevated temperaturesto give 2b.

An alternate route for the preparation of Compound IIIb wherein X is Nis illustrated in Scheme 5. Compound 12 is prepared according to themethod outlined above employing dichloropyrazine 10 instead ofchloropyrazine 6. Compound 12 is then subjected to catalytichydrogenation using a catalyst such as platinum oxide to provideCompound IIIb, as its monohydrochloride salt.

Intermediates II and III are coupled under standard peptide couplingconditions, for example, using1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC),1-hydroxybenzotriazole (HOBT), and a base, generallydiisopropylethylamine, in a solvent such as N,N-dimethylformamide (DMF)or dichloromethane for 3 to 48 hours at ambient temperature to provideintermediate 13 as shown in Scheme 6. The protecting group is thenremoved with, for example, trifluoroacetic acid or methanolic hydrogenchloride in the case of Boc to give the desired amine I. The product ispurified from unwanted side products, if necessary, byrecrystallization, trituration, preparative thin layer chromatography,flash chromatography on silica gel as described by W. C. Still et al, J.Org. Chem., 43, 2923 (1978), or HPLC. Compounds which are purified byHPLC may be isolated as the corresponding salt. Purification ofintermediates is achieved in the same manner.

In some cases the intermediate 13 from the coupling reaction describedin Scheme 6 may be further modified before removal of the protectinggroup, for example, by manipulation of substituents on X or R¹. Thesemanipulations may include, but are not limited to, reduction, oxidation,alkylation, acylation, and hydrolysis reactions which are commonly knownto those skilled in the art.

In some cases the order of carrying out the foregoing reaction schemesmay be varied to facilitate the reaction or to avoid unwanted reactionproducts. The following examples are provided so that the inventionmight be more fully understood. These examples are illustrative only andshould not be construed as limiting the invention in any way.

Intermediate 1

(3R)-3-[(1,1-Dimethylethoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoicacid Step A.(R,S)—N-(1,1-Dimethylethoxycarbonyl)-2,5-difluorophenylalanine

To a solution of 0.5 g (2.49 mmol) of 2,5-difluoro-DL-phenylalanine in 5mL of tert-butanol were added sequentially 1.5 mL of 2N aqueous sodiumhydroxide solution and 543 mg of di-tert-butyl dicarbonate. The reactionwas stirred at ambient temperature for 16 h and diluted with ethylacetate. The organic phase was washed sequentially with 1N hydrochloricacid and brine, dried over magnesium sulfate and concentrated in vacuo.The crude material was purified by flash chromatography (silica gel,97:2:1 dichloromethane:methanol:acetic acid) to afford 671 mg of thetitle compound. MS 302 (M+1).

Step B.(R,S)-3-[(1,1-Dimethylethoxycarbonyl)amino]-1-diazo-4-(2,5-difluorophenyl)butan-2-one

To a solution of 2.23 g (7.4 mmol) of(R,S)—N-(1,1-dimethylethoxycarbonyl)-2,5-difluorophenylalanine in 100 mLof diethyl ether at 0° C. were added sequentially 1.37 mL (8.1 mmol) oftriethylamine and 0.931 mL (7.5 mmol) of isobutyl chloroformate and thereaction was stirred at this temperature for 15 min. A cooled etherealsolution of diazomethane was then added until the yellow color persistedand stirring was continued for a further 16 h. The excess diazomethanewas quenched by dropwise addition of acetic acid, and the reaction wasdiluted with ethyl acetate and washed sequentially with 5% hydrochloricacid, saturated aqueous sodium bicarbonate solution and brine, driedover magnesium sulfate and concentrated in vacuo. Purification by flashchromatography (silica gel, 4:1 hexane:ethyl acetate) afforded 1.5 g ofdiazoketone. ¹H NMR (500 MHz, CDCl₃) δ 7.03-6.95 (m, 1H), 6.95-6.88 (m,2H), 5.43 (bs, 1H), 5.18 (bs, 1H), 4.45 (bs, 1H), 3.19-3.12 (m, 1H),2.97-2.80 (m, 1H), 1.38 (s, 9H).

Step C.(3R)-3-[(1,1-Dimethylethoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoicacid

To a solution of 2.14 g (6.58 mmol) of(R,S)-3-[(1,1-dimethylethoxycarbonyl)-amino]-1-diazo-4-(2,5-difluorophenyl)butan-2-onedissolved in 100 mL of methanol at −30° C. were added sequentially 3.3mL (19 mmol) of diisopropylethylamine and 302 mg (1.32 mmol) of silverbenzoate. The reaction was stirred for 90 min before diluting with ethylacetate and washing sequentially with 2N hydrochloric acid, saturatedaqueous sodium bicarbonate, and brine. The organic phase was dried overmagnesium sulfate, concentrated in vacuo and the enantiomers wereseparated by preparative chiral HPLC (Chiralpak AD column, 5% ethanol inhexanes) to give 550 mg of the desired (R)-enantiomer, which elutedfirst. This material was dissolved in 50 mL of a mixture oftetrahydrofuran:methanol:1N aqueous lithium hydroxide (3:1:1) andstirred at 50° C. for 4 h. The reaction was cooled, acidified with 5%dilute hydrochloric acid and extracted with ethyl acetate. The combinedorganic phases were washed with brine, dried over magnesium sulfate andconcentrated in vacuo to give 360 mg of the title compound as a whitefoamy solid. ¹H NMR (500 MHz, CDCl₃) δ 7.21 (m, 1H), 6.98 (m, 2H), 6.10(bs, 1H), 5.05 (m, 1H), 4.21 (m, 1H), 2.98 (m, 2H), 2.60 (m, 2H), 1.38(s, 9H).

Intermediate 2

(3R)-3-[(1,1-Dimethylethoxycarbonyl)amino]-4-[2-fluoro-4-(trifluoromethyl)phenyl]-butanoicacid Step A.(2R,5S)-2,5-Dihydro-3,6-dimethoxy-2-(2′-fluoro-4′-(trifluoromethyl)benzyl)-5-isopropylpyrazine

To a solution of 3.32 g (18 mmol) of commercially available(2S)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine in 100 mL oftetrahydrofuran at −70° C. was added 12 mL (19 mmol) of a 1.6M solutionof butyllithium in hexanes. After stirring at this temperature for 20min, 5 g (19.5 mmol) of 2-fluoro-4-trifluoromethylbenzyl bromide in 20mL of tetrahydrofuran was added and stirring was continued for 3 hbefore warming the reaction to ambient temperature. The reaction wasquenched with water, concentrated in vacuo, and extracted with ethylacetate. The combined organic phase was washed with brine, dried, andconcentrated in vacuo. Purification by flash chromatography (silica gel,0-5% ethyl acetate in hexanes) afforded 5.5 g of the title compound. ¹HNMR (500 MHz, CDCl₃) δ 7.33-7.25 (m, 3H), 4.35-4.31 (m, 1H), 3.75 (s,3H), 3.65 (s, 3H), 3.60 (t, 1H, J=3.4 Hz), 3.33 (dd, 1H, J=4.6, 13.5Hz), 3.03 (dd, 1H, J=7, 13.5 Hz), 2.25-2.15 (m, 1H), 1.0 (d, 3H, J=7Hz), 0.66 (d, 3H, J=7 Hz).

Step B.(R)—N-(1,1-Dimethylethoxycarbonyl)-2-fluoro-4-trifluoromethyl)phenylalaninemethyl ester

To a solution of 5.5 g (15 mmol) of(2R,5S)-2,5-dihydro-3,6-dimethoxy-2-(2′-fluoro-4′-(trifluoromethyl)benzyl)-5-isopropylpyrazinein 50 mL of a mixture of acetonitrile:dichloromethane (10:1) was added80 mL of 1N aqueous trifluoroacetic acid. The reaction was stirred for 6h and the organic solvents were removed in vacuo. Sodium carbonate wasadded until the solution was basic (>pH 8), and then the reaction wasdiluted with 100 mL of tetrahydrofuran and 10 g (46 mmol) ofdi-tert-butyl dicarbonate was added. The resulting slurry was stirredfor 16 h, concentrated in vacuo, and extracted with ethyl acetate. Thecombined organic phase was washed with brine, dried, and concentrated invacuo. Purification by flash chromatography (silica gel, 20% ethylacetate in hexanes) afforded 5.1 g of the title compound. ¹H NMR (500MHz, CDCl₃) δ 7.38-7.28 (m, 3H), 5.10 (bd, 1H), 4.65-3.98 (m, 1H), 3.76(s, 3H), 3.32-3.25 (m, 1H), 3.13-3.05 (m, 1H), 1.40 (s, 9H).

Step C.(R)—N-(1,1-Dimethylethoxycarbonyl)-2-fluoro-4-trifluoromethyl)phenylalanine

A solution of 5.1 g (14 mmol) of(R,S)—N-(1,1-dimethylethoxycarbonyl)-2-fluoro-4-trifluoromethyl)phenylalaninemethyl ester in 350 mL of a mixture of tetrahydrofuran:methanol:1Nlithium hydroxide (3:1:1) was stirred at 50° C. for 4 h. The reactionwas cooled, acidified with 5% dilute hydrochloric acid and extractedwith ethyl acetate. The combined organic phases were washed with brine,dried over magnesium sulfate and concentrated in vacuo to give 4.8 g ofthe title compound. ¹H NMR (500 MHz, CD₃OD) δ 7.45-7.38 (m, 3H),4.44-4.40 (m, 1H), 3.38-3.33 (m, 1H), 2.98 (dd, 1H, J=9.6, 13.5 Hz),1.44 (s, 9H).

Step D.(3R)-3-[(1,1-Dimethylethoxycarbonyl)amino]-4-[2-fluoro-4-(trifluoromethyl)-phenyl]butanoicacid

To a solution of 3.4 g (9.7 mmol) of the product from Step C in 60 mL oftetrahydrofuran at 0° C. were added sequentially 2.3 mL (13 mmol) ofdiisopropylethylamine and 1.7 mL (13 mmol) of isobutyl chloroformate andthe reaction was stirred at this temperature for 30 min. A cooledethereal solution of diazomethane was then added until the yellow colorpersisted and stirring was continued for a further 16 h. The excessdiazomethane was quenched by dropwise addition of acetic acid, and thereaction was diluted with ethyl acetate and washed sequentially with 5%hydrochloric acid, saturated aqueous sodium bicarbonate solution andbrine, dried over magnesium sulfate and concentrated in vacuo.Purification by flash chromatography (silica gel, 9:1 hexane:ethylacetate) afforded 0.5 g of diazoketone. To a solution of 0.5 g (1.33mmol) of the diazoketone dissolved in 100 mL of methanol at 0° C. wereadded sequentially 0.7 mL (4 mmol) of diisopropylethylamine and 32 mg(0.13 mmol) of silver benzoate. The reaction was stirred for 2 h beforediluting with ethyl acetate and washing sequentially with 2Nhydrochloric acid, saturated aqueous sodium bicarbonate, and brine. Theorganic phase was dried over magnesium sulfate, concentrated in vacuoand dissolved in 50 mL of a mixture of tetrahydrofuran:methanol:1Naqueous lithium hydroxide (3:1:1) and stirred at 50° C. for 3 h. Thereaction was cooled, acidified with 5% dilute hydrochloric acid andextracted with ethyl acetate. The combined organic phases were washedwith brine, dried over magnesium sulfate and concentrated in vacuo togive 410 mg of the title compound as a white foamy solid. ¹H NMR (500MHz, CD₃OD) δ 7.47-7.33 (m, 3H), 4.88 (bs, 1H), 4.26-3.98 (m, 1H),3.06-3.01 (m, 1H), 2.83-2.77 (m, 1H), 2.58-2.50 (m, 2H), 1.29 (s, 9H).

Intermediate 3

(3R)-3-[(1,1-Dimethylethoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid Step A.(2S,5R)-2,5-Dihydro-3,6-dimethoxy-2-isopropyl-5-(2′,4′,5′trifluorobenzyl)pyrazine

The title compound (3.81 g) was prepared from 3.42 g (18.5 mmol) of(2S)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine using the proceduredescribed for Intermediate 2, Step A. ¹H NMR (500 MHz, CDCl₃) δ 7.01 (m,1H), 6.85 (m, 1H), 4.22 (m, 1H), 3.78 (m, 3H), 3.64 (m, 3H), 3.61 (m,1H), 3.20 (m, 1H), 2.98 (m, 1H), 2.20 (m, 1H), 0.99 (d, 3H, J=8 Hz),0.62 (d, 3H, J=8 Hz).

Step B. (R)—N-(1,1-Dimethylethoxycarbonyl)-2,4,5-trifluorophenylalaninemethyl ester

To a solution of 3.81 g (11.6 mmol) of(2S,5R)-2,5-dihydro-3,6-dimethoxy-2-isopropyl-5-(2′,4′,5′trifluoro-benzyl)pyrazinein 20 mL of acetonitrile was added 20 mL of 2N hydrochloric acid. Thereaction was stirred for 72 h and concentrated in vacuo. The residue wasdissolved in 30 mL of dichloromethane and 10 mL (72 mmol) oftriethylamine and 9.68 g (44.8 mmol) of di-tert-butyldicarbonate wereadded. The reaction was stirred for 16 h, diluted with ethyl acetate andwashed sequentially with 1N hydrochloric acid and brine. The organicphase was dried over sodium sulfate, concentrated in vacuo and purifiedby flash chromatography (silica gel, 9:1 hexanes:ethyl acetate) toafford 2.41 g of the title compound. ¹H NMR (500 MHz, CDCl₃) δ 6.99 (m,1H), 6.94 (m, 1H), 5.08 (m, 1H), 4.58 (m, 1H), 3.78 (m, 3H), 3.19 (m,1H), 3.01 (m, 1H), 1.41 (s, 9H).

Step C. (R)—N-(1,1-Dimethylethoxycarbonyl)-2,4,5-trifluorophenylalanine

The title compound (2.01 g) was prepared from 2.41 g (7.5 mol) of(R)—N-(1,1-dimethylethoxycarbonyl)-2,4,5-trifluorophenylalanine methylester using the procedure described for Intermediate 2, Step C. MS(M+1)-BOC 220.9.

Step D.(3R)-3-[(1,1-Dimethylethoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid

To a solution of 0.37 g (1.16 mmol) of(R)—N-(1,1-dimethylethoxycarbonyl)-2,4,5-trifluorophenylalanine in 10 mLof diethyl ether at −20° C. were added sequentially 0.193 mL (1.3 mmol)of triethylamine and 0.18 mL (1.3 mmol) of isobutyl chloroformate, andthe reaction was stirred at this temperature for 15 min. A cooledethereal solution of diazomethane was then added until the yellow colorpersisted and stirring was continued for a further 1 h. The excessdiazomethane was quenched by dropwise addition of acetic acid, and thereaction was diluted with ethyl acetate and washed sequentially withsaturated aqueous sodium bicarbonate solution and brine, dried overmagnesium sulfate and concentrated in vacuo. Purification by flashchromatography (silica gel, 3:1 hexane:ethyl acetate) afforded 0.36 g ofdiazoketone. To a solution of 0.35 g (1.15 mmol) of the diazoketonedissolved in 12 mL of 1,4-dioxane:water (5:1) was added 26 mg (0.113mmol) of silver benzoate. The resultant solution was sonicated for 2 hbefore diluting with ethyl acetate and washing sequentially with 1Nhydrochloric acid and brine, drying over magnesium sulfate andconcentrating in vacuo. Purification by flash chromatography (silicagel, 97:2:1 dichloromethane:methanol:acetic acid) afforded 401 mg of thetitle compound. ¹H NMR (500 MHz, CDCl₃) δ 7.06 (m, 1H), 6.95 (m, 1H),5.06 (bs, 1H), 4.18 (m, 1H), 2.98 (m, 2H), 2.61 (m, 2H), 1.39 (s, 9H).

Intermediate 4

(3R)-3-[(1,1-Dimethylethoxycarbonyl)amino]-4-(4-bromo-2,5-difluorophenyl)butanoicacid Step A. 4-Bromo-2,5-difluorobenzyl bromide

To a solution of 2 g (8.44 mmol) of 4-bromo-2,5-difluorobenzoic acid(prepared according to the procedure of Ishikawa et al., Kogyo KagakuZasshi, pg 972-979, 1970) in 20 mL of tetrahydrofuran was added 40 mL ofa 1M solution of borane-tetrahydrofuran complex. The solution was heatedunder reflux for 64 h, cooled to ambient temperature and 100 mL ofmethanol was added. The reaction was then heated for a further 2 h,cooled and concentrated in vacuo. Purification by flash chromatography(silica gel, 9:1 hexane:ethyl acetate) afforded 1.6 g of4-bromo-2,5-difluorobenzyl alcohol. To a solution of 1.3 g (5.6 mmol) of4-bromo-2,5-difluorobenzyl alcohol in 20 mL of dichloromethane at 0° C.was added 2.27 g (6.7 mmol) of carbon tetrabromide and 1.8 g (6.7 mmol)of triphenylphosphine. The reaction was stirred for 2 h at thistemperature, the solvent was removed in vacuo and the residue stirredwith 100 mL of diethyl ether. The solution was filtered, concentrated invacuo, and purified by flash chromatography (silica gel, 9:1hexane:ethyl acetate) to afford 1.5 g of the title compound.

Step B.(2S,5R)-2,5-Dihydro-3,6-dimethoxy-2-isopropyl-5-(4′-bromo-2′,5′-difluorobenzyl)pyrazine

The title compound (1.61 g) was prepared from 0.865 g (4.7 mmol) of(2S)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine and 1.5 g (5.2 mmol)of 4-bromo-2,5-difluorobenzyl bromide using the procedure described forIntermediate 2, Step A. ¹H NMR (400 MHz, CDCl₃) δ 7.21 (m, 1H), 6.97 (m,1H), 4.25 (m, 1H), 3.78 (s, 3H), 3.70-3.64 (m, 4H), 3.25-3.18 (m, 1H),2.96-2.90 (m, 1H), 2.25-2.16 (m, 1H), 1.01 (d, 3H, J=8 Hz), 0.65 (d, 3H,J=8 Hz).

Step C.(R)—N-(1,1-Dimethylethoxycarbonyl)-4-bromo-2,5-difluorophenylalaninemethyl ester

To a solution of 1.61 g (4.14 mmol) of(2S,5R)-2,5-dihydro-3,6-dimethoxy-2-isopropyl-5-(4′-bromo-2′,5′-difluorobenzyl)pyrazinein 10 mL of acetonitrile was added 10 mL of 2N hydrochloric acid. Thereaction was stirred for 16 h and concentrated in vacuo. The residue wasdissolved in 30 mL of dichloromethane and 5.6 mL (40 mmol) oftriethylamine and 2.2 g (10 mmol) of di-tert-butyldicarbonate wereadded. The reaction was stirred for 16 h, diluted with ethyl acetate andwashed sequentially with saturated aqueous sodium bicarbonate solutionand brine. The organic phase was dried over magnesium sulfate,concentrated in vacuo and purified by flash chromatography (silica gel,9:1 hexanes:ethyl acetate) to afford 1.22 g of the title compound. ¹HNMR (400 MHz, CDCl₃) δ 7.27-7.15 (m, 1H), 6.98-6.93 (m, 1H), 5.08 (bs,1H), 4.61-4.55 (m, 1H), 3.78 (s, 3H), 3.23-3.18 (m, 1H), 3.05-2.95 (m,1H), 1.41 (s, 9H).

Step D.(R)—N-(1,1-Dimethylethoxycarbonyl)-4-bromo-2,5-difluorophenylalanine

The title compound (1.34 g) was prepared from 1.4 g (3.5 mmol) of(R)—N-(1,1-dimethylethoxycarbonyl)-4-bromo-2,5-difluorophenylalaninemethyl ester using the procedure described for Intermediate 2, Step C.MS (M+1) 380.3 and 382.3.

Step E.(3R)-3-[(1,1-Dimethylethoxycarbonyl)amino]-4-(4′-bromo-2′,5′-difluorophenyl)butanoicacid

The title compound (0.36 g) was prepared from 0.6 g (1.57 mmol) of(R)—N-(1,1-dimethylethoxycarbonyl)-4-bromo-2,5-difluorophenylalanineusing the procedure described for Intermediate 3, Step D. MS (M+1) 394.1and 396.1.

Example 1

7-[(3R)-3-Amino-4-(3,4-difluorophenyl)butanoyl]-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,dihydrochloride Step A. 2-(Trifluoromethyl)imidazo[1,2-a]pyrazine

To a solution of 2-aminopyrazine (5.25 g, 55.2 mmol) in ethanol (120 mL)was added 1-bromo-3,3,3-trifluoroacetone (5.73 mL, 55.2 mmol). Thereaction was stirred at reflux for 20 h. After evaporation of solvent,the residue was partitioned between ethyl acetate and saturated aqueoussodium bicarbonate solution. The aqueous layer was extracted with ethylacetate (3×). The combined organic phase was washed with brine, driedover magnesium sulfate and concentrated. The residue was purified byflash chromatography (silica gel, 1:1 ethyl acetate:hexane, then 100%ethyl acetate) to give 2.35 g of the title compound as a solid. ¹H NMR(500 MHz, CDCl₃) δ 8.02 (m, 2H), 8.13 (m, 1H), 9.22 (s, 1H). ESI-MS 188(M+1).

Step B. 2-(Trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

To a solution of 2-(trifluoromethyl)imidazo[1,2-a]pyrazine (2.0 g, 10.46mmol, from Step A) in methanol (100 mL) was added 10% palladium oncarbon (400 mg). The mixture was stirred under atmospheric hydrogen atambient temperature for 14 h. The mixture was filtered through Celiteand washed with methanol (3×). The filtrate was concentrated andpurified by flash chromatography (silica gel, 10% methanol in ethylacetate, then 15% methanol in chloroform with 1% aqueous ammoniumhydroxide) to give 1.33 g of the title compound as a solid. ¹H NMR (500MHz, CDCl₃) δ 1.93 (bs, 1H), 3.26 (t, 2H, J=5.5 Hz), 3.99 (t, 2H, J=5.5Hz), 4.10 (s, 1H), 7.16 (s, 1H). ESI-MS 192 (M+1).

Step C.7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(3,4-difluorophenyl)butanoyl]-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

To a solution of2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine (64.3 mg,0.34 mmol, from Step B) and(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(3,4-difluorophenyl)butanoicacid (105.9 mg, 0.34 mmol) in dichloromethane (5 mL) was added HOBT(54.5 mg, 0.42 mmol) at 0° C. The reaction was stirred at 0° C. for 10min, then EDC (96.6 mg, 0.50 mmol) was added. After removal of theice-bath, the reaction was allowed to stir at ambient temperature for 14h. The mixture was concentrated and purified by HPLC (Gilson; YMC-PackPro C18 column, 100×20 mm I.D.; solvent gradient from 10% acetonitrile,90% water, and 0.1% trifluoroacetic acid to 90% acetonitrile, 10% water,and 0.1% trifluoroacetic acid) to give 115 mg of the title compound as afoamy solid. ¹H NMR (500 MHz, CDCl₃) δ 1.36 (s, 9H), 2.62 (m, 2H), 2.86(m, 2H) 3.34 (bs, 1H), 3.86 (m, 1H), 4.05 (m, 4H). 4.85 (m, 1H)5.30-5.38 (m, 1H) 6.97 (m, 3H), 7.28 (m, 1H). LC/MS 489 (M+1).

Step D.7-[(3R)-3-Amino-4-(3,4-difluorophenyl)butanoyl]-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,dihydrochloride

To7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(3,4-difluorophenyl)butanoyl]-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(110.8 mg, 0.226 mmol, from Step C) was added 2 mL of methanol saturatedwith hydrogen chloride. The reaction was stirred at ambient temperaturefor 1 h. Concentration gave 89.5 mg of the title compound as a foamysolid. ¹H NMR (500 MHz, CD₃OD) δ 2.97-3.10 (m, 4H), 3.91-4.34 (m, 5H),4.90-5.04 (m, 2H), 7.16-7.33 (m, 2H), 8.01-8.08 (m, 1H). ESI-MS 389(M+1).

Example 2

7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,dihydrochloride Step A.7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

The title compound was prepared from2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine (277 mg,1.45 mmol, from Example 1, Step B),(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoicacid (Intermediate 1, 416 mg, 1.32 mmol), DIPEA (226 mg, 1.58 mol), HOBT(216 mg, 1.98 mol) and HATU (753 mg, 1.98 mol) in DMF (6 mL), using aprocedure analogous to that described in Example 1 Step C, except forthe purification method. The compound was purified by preparative TLC(silica gel, 20% hexane in ethyl acetate, then 10% methanol indichloromethane) to give 360 mg of the title compound as a foamy solid.¹H NMR (500 MHz, CDCl₃) δ 1.35 (s, 9H), 2.62 (m, 2H), 2.88 (m, 2H)3.88-4.16 (m, 5H), 4.73 (s, 1H), 4.85 (m, 1H) 5.26-5.39 (m, 1H) 6.90(bs, 1H), 7.06 (m, 2H), 7.24 (m, 1H). ESI-MS 489 (M+1).

Step B.7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,dihydrochloride

The title compound was prepared from7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)-amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(349.8 mg, 0.72 mol, from Step A) in 1.5 mL of methanol saturated withhydrogen chloride, using a procedure analogous to that described inExample 1, Step D. Evaporation of solvent gave 299 mg of the titlecompound as a foamy solid. ¹H NMR (500 MHz, CD₃OD): δ 3.10-3.17 (m, 2H),2.89-2.99 (m, 2H), 3.94-4.22 (m, 4H), 4.33 (m, 1H), 4.91-5.48 (m, 2H),7.07-7.23 (m, 3H), 8.05 (m, 1H). ESI-MS 389 (M+1).

Example 3

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,dihydrochloride Step A.7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

The title compound was prepared from2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine (31.7 mg,0.166 mmol, from Example 1, Step B),(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3, 57 mg, 0.166 mmol), HOBT (26.9 mg, 0.199) mmol,and EDC (47.8 mg, 0.249 mmol) in 4 mL of dichloromethane, using aprocedure analogous to that described in Example 1, Step C. Purificationby preparative TLC (silica gel, 100% ethyl acetate, then 10% methanol indichloromethane) gave 40 mg of the title compound as a foamy solid. ¹HNMR (500 MHz, CDCl₃) δ 1.35 (s, 9H), 3.00 (m, 2H), 3.30 (m, 2H), 3.93(m, 1H) 4.04-4.24 (m, 2H), 4.23 (s, 1H), 4.35 (m, 1H) 4.97-5.48 (m, 2H)7.22 (m, 1H), 7.44 (m, 1H), 8.04 (m, 1H). ESI-MS 507 (M+1).

Step B.7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,dihydrochloride

The title compound was prepared from7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(38 mg, 0.075 mmol, from Step A), in 1.5 mL of methanol saturated withhydrogen chloride, using a procedure analogous to that described inExample 1, Step D. Evaporation of solvent gave 34 mg of the titlecompound as a foamy solid. ¹H NMR (500 MHz, CD₃OD): δ 2.59-2.66 (m, 2H),2.92 (m, 2H), 3.89-4.16-4.22 (m, 5H), 4.70-4.84 (m, 2H), 5.42 (m, 1H),6.86 (m, 1H), 7.06 (m, 1H), 7.24 (m, 1H). ESI-MS 407 (M+1).

Example 4

7-[(3R)-3-Amino-4-(3,4-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,dihydrochloride Step A. Imidazo[1,2-a]pyrazine

To a solution of 2-aminopyrazine (2.0 g, 21.03 mmol) in ethanol (40 mL)was added 2-bromo-1,1-dimethoxyethane (2.5 mL, 21.03 mmol) followed by 5drops of concentrated hydrochloric acid. After refluxing for 14 hours,the solvent was evaporated. The residue was partitioned between ethylacetate and saturated aqueous sodium bicarbonate solution. The aqueouslayer was extracted with ethyl acetate (3×). The combined organic phasewas washed with brine, dried over magnesium sulfate, and concentrated.The residue was purified by flash chromatography (100% ethyl acetate,10% methanol in ethyl acetate, then 10% methanol in dichloromethane) togive 536 mg of the title compound as a solid. ¹H NMR (500 MHz, CDCl₃) δ7.70 (bs, 1H), 7.82 (bs, 1H), 7.89 (d, 1H, J=4.4 Hz), 8.10 (d, 1H, J=4.6Hz), 9.12 (s, 1H).

Step B. 5,6,7,8-Tetrahydroimidazo[1,2-a]pyrazine

The title compound was prepared from imidazo[1,2-a]pyrazine (500 mg,4.20 mmol, from Step A) and platinum oxide (250 mg) in methanol (50 mL),using a procedure analogous to that described in Example 1, Step B.Concentration gave the title compound (512 mg) as a viscous oil. ¹H NMR(500 MHz, CD₃OD) δ 3.37 (t, 1H, J=5.5 Hz), 4.18 (t, 2H, J=5.6 Hz), 4.88(s, 1H), 7.27 (d, J=1.6 Hz, 1H), 7.33 (d, 1H).

Step C.7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(3,4-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

The title compound was prepared from5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine (31.3 mg, 0.254 mmol, from StepB),(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(3,4-difluorophenyl)butanoicacid (80 mg, mmol), DIPEA (32.8 mg, 0.254 mmol), HOBT (41.2 mg, 0.305mmol) and EDC (73 mg, 0.381 mmol) in 5 mL of dichloromethane, using aprocedure analogous to that described in Example 1, Step C. Purificationby HPLC (Gilson; YMC-Pack Pro C18 column, 100×20 mm I.D.; solventgradient system from 10% acetonitrile, 90% water, and 0.1%trifluoroacetic acid to 90% acetonitrile, 10% water, and 0.1%trifluoroacetic acid) gave 75 mg of the title compound as a viscous oil.¹H NMR (500 MHz, CDCl₃) δ 1.38 (s, 9H), 2.05 (bs, 1H), 2.62 (m, 2H),2.89 (m, 2H) 3.81-4.04 (m, 5H), 4.64-4.88 (m, 2H). 5.38 (m, 1H) 6.88 (m,2H), 7.05 (m, 3H). ESI-MS 421 (M+1).

Step D.7-[(3R)-3-Amino-4-(3,4-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,dihydrochloride

The title compound was prepared from7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)-amino]-4-(3,4-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(72 mg, 0.171 mmol, from Step C), in 1.5 mL of methanol saturated withhydrogen chloride, using a procedure analogous to that described inExample 1, Step D. Concentration gave 66 mg of the title compound as afoamy solid. ¹H NMR (500 MHz, CD₃OD) δ 2.96-3.13 (m, 4H), 3.93 (m, 1H),4.13 (m, 2H), 4.26-4.38 (m, 2H), 4.26-4.38 (m, 2H), 4.90-5.04 (m, 2H),7.19-7.36 (m, 3H), 7.58 (m, 1H). ESI-MS 321 (M+1).

Example 5

7-[(3R)-3-Amino-4-(3,4-difluorophenyl)butanoyl]-3-ethyl-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine,dihydrochloride Step A. 8-Chloro-3-ethyl-1,2,4-triazolo[4,3-a]pyrazine

To 3-chloro-2-hydrazinopyrazine (3.0 g, 20.75 mmol), prepared from2,3-dichloropyrazine and hydrazine using a procedure analogous to thatdescribed in the literature (Huynh-Dinh et al, J. Org. Chem. 1979, 44,1028), was added 8 mL of triethyl orthopropionate. After refluxing for10 h, the reaction was cooled down to ambient temperature and theprecipitate was filtered. The solid was purified by flash chromatography(100% ethyl acetate, then 10% methanol in ethyl acetate) to give 2.73 gof the title compound as a solid. ¹H NMR (500 MHz, CDCl₃) δ 1.54 (t, 3H,J=7.6 Hz), 3.16 (q, 2H, J=7.8 Hz), 7.70 (d, 1H, J=4.5 Hz), 7.83 (d, 1H,J=4.8 Hz).

Step B. 3-Ethyl-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine,hydrochloride

The title compound was prepared from8-chloro-3-ethyl-1,2,4-triazolo[4,3-a]pyrazine (2.70 g, 14.8 mmol, fromStep A) and platinum oxide (0.4 g) in 200 mL of methanol in a paarshaker under hydrogen (50 psi) for 14 hours. Filtration through Celitefollowed by concentration gave the title compound as a solid. ¹H NMR(500 MHz, CD₃OD) δ 1.36 (t, 3H, J=6.0 Hz), 2.84 (q, 2H, J=6.0 Hz), 3.70(t, 2H, J=8.0 Hz), 4.28 (t, 2H, J=8.0 Hz). 4.06 (s, 2H). ESI-MS 153(M+1).

Step C.7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(3,4-difluorophenyl)butanoyl]-3-ethyl-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

The title compound was prepared from3-ethyl-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine hydrochloride(400 mg, 2.12 mmol, from Step B),(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(3,4-difluorophenyl)butanoicacid (668 mg, 2.12 mmol), DIPEA (1.1 mL, 4.24 mmol), HOBT (343.8 mg,2.54 mmol) and EDC (609.6 mg, 3.18 mmol) in 20 mL of dichloromethane,using a procedure analogous to that described in Example 1, Step C. Thecrude product was purified by HPLC (Gilson; YMC-Pack Pro C18 column,100×20 mm I.D.; solvent gradient from 10% acetonitrile, 90% water, and0.1% trifluoroacetic acid to 90% acetonitrile, 10% water, and 0. %trifluoroacetic acid) to give 366.3 mg of the title compound as aviscous oil. ¹H NMR (500 MHz, CDCl₃) δ 1.31-1.34 (m, 12H), 2.67-2.92 (m,6H), 4.03-4.12 (m, 4H), 5.03-5.31 (m, 3H), 6.93 (s, 1H), 7.05 (m, 2H).ESI-MS 450 (M+1).

Step D.7-[(3R)-3-Amino-4-(3,4-difluorophenyl)butanoyl]-3-ethyl-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine,dihydrochloride

The title compound was prepared from7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)-amino]-4-(3,4-difluorophenyl)butanoyl]-3-ethyl-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine(30 mg, 0.067 mmol from Step C), in 1.5 mL of methanol saturated withhydrogen chloride, using a procedure analogous to that described inExample 1, Step D. Evaporation of solvent afforded 28 mg of the titlecompound as a viscous oil. ¹H NMR (500 MHz, CD₃OD) δ 1.45 (t, 3H),2.93-3.07 (m, 6H), 3.90-4.31 (m, 5H), 5.08 (m, 2H), 7.16 (s, 1H), 7.31(m, 2H). ESI-MS 350 (M+H).

Example 6

7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine,hydrochloride Step A. 3-(Trifluoromethyl)-1,2,4-triazolo[4,3-a]pyrazine

A mixture of 2-hydrazinopyrazine (820 mg, 7.45 mmol), prepared from2-chloropyrazine and hydrazine using a procedure analogous to thatdescribed in the literature (P. J. Nelson and K. T. Potts, J. Org. Chem.1962, 27, 3243, except that the crude product was extracted into 10%methanol/dichloromethane and filtered, and the filtrate was concentratedand purified by flash chromatography on silica gel, eluting with 100%ethyl acetate followed by 10% methanol in dichloromethane), TFA (2.55 g,22.4 mmol), and polyphosphoric acid (10 mL) was heated to 140° C. withstirring for 18 h. The solution was added to ice and neutralized by theaddition of ammonium hydroxide. The aqueous solution was extracted withethyl acetate (3×), washed with brine, and dried over anhydrousmagnesium sulfate. Concentration followed by flash chromatography(silica gel, 1:1 hexane:ethyl acetate, then 100% ethyl acetate) affordedthe title compound as a solid (861 mg). ¹H NMR (500 MHz, CDCl₃) δ8.17˜8.20 (m, 2H), 9.54 (s, 1H). LC/MS (M+1) 189.

Step B.3-(Trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

3-(Trifluoromethyl)-1,2,4-triazolo[4,3-a]pyrazine (540 mg, 2.87 mmol,from Step A) was hydrogenated under atmospheric hydrogen with 10% Pd/C(200 mg) as a catalyst in ethanol (10 mL) at ambient temperature for 18h. Filtration through Celite followed by concentration gave a darkcolored oil. Dichloromethane was added to the above oil and theinsoluble black precipitate was filtered off. Concentration of thefiltrate gave the title compound as an oil (495 mg). ¹H NMR (500 MHz,CDCl₃) δ 2.21 (br, 1H), 3.29 (t, 2H, J=5.5 Hz), 4.09 (t, 2H, J=5.5 Hz),4.24 (s, 2H). LC/MS (M+1) 193.

Step C.7-[(3R)-3-[(1,1-Dimethylethoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

The title compound was prepared from(3R)-3-[(1,1-dimethylethoxycarbonyl)-amino]-4-(2,5-difluorophenyl)butanoicacid (Intermediate 1, 50 mg, 0.16 mmol) and3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine (30mg, 0.16 mmol) using a procedure analogous to that described for Example1, Step C. The crude product was purified by preparative TLC (silicagel, 100% ethyl acetate, then 10% methanol/dichloromethane (2×)) toafford the title compound (38.1 mg) as a solid. ¹H NMR (500 MHz, CDCl₃)δ 1.38 (s, 9H), 2.57˜3.05 (m, 4H), 3.85˜4.30 (m, 5H), 4.90 (s, 1H),4.95˜5.15 (m, 1H), 5.22˜5.40 (br, 1H), 6.86˜7.24 (m, 3H). LC/MS(M+1-t-Boc) 390.

Step D. 7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine,hydrochloride

The title compound was prepared from7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)-amino]-4-(2,5-difluorophenyl)butanoyl]-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine(19.1 mg, 0.039 mmol, from Step C) using a procedure analogous to thatdescribed for Example 1, Step D. Concentration afforded the titlecompound (16.1 mg) as a solid. ¹H NMR (500 MHz, CD₃OD) δ 2.75˜3.16 (m,4H), 3.86˜4.35 (m, 5H), 4.95˜5.05 (m, 2H), 7.03˜7.20 (m, 3H). LC/MS(M+1) 390.

Example 7

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine,hydrochloride Step A.7-[(3R)-3-[(1,1-Dimethylethoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

The title compound was prepared from(3R)-3-[(1,1-dimethylethoxycarbonyl)-amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3, 50.1 mg, 0.15 mmol) and3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine(39.2 mg, 0.20 mmol) using a procedure analogous to that described forExample 1, Step C. The crude product was purified by preparative TLC(silica gel, 100% ethyl acetate) to afford the title compound (29 mg) asa solid. ¹H NMR (500 MHz, CDCl₃) δ 1.37 (s, 9H), 2.61˜3.00 (m, 4H),3.92˜4.30 (m, 5H), 4.93 (s, 1H), 4.95˜5.12 (m, 1H), 5.22˜5.35 (br, 1H),6.83˜6.95 (m, 1H), 7.02˜7.12 (m, 1H). LC/MS (M+1-t-Bu) 452.

Step B.7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine,hydrochloride

The title compound was prepared from7-[(3R)-3-[(1,1-dimethylethoxycarbonyl)-amino]-4-(2,4,5-trifluorophenyl)butanoyl]-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine(22 mg, 0.039 mmol, from Step A) using a procedure analogous to thatdescribed for Example 1, Step D. Concentration afforded the titlecompound (16.5 mg) as a solid. ¹H NMR (500 MHz, CD₃OD) δ 2.75˜3.15 (m,4H), 3.82˜4.35 (m, 5H), 4.90˜5.05 (m, 2H), 7.16˜7.25 (m, 1H), 7.30˜7.42(m, 1H). LC/MS (M+1) 408.

Essentially following the procedures outlined for Examples 1-7, thecompounds listed in Table 1 were prepared.

TABLE 1

Example R³ X R¹ MS (M + 1) 8 2-F C—Et H 331 9 3-F, 4-F C—Et H 349 10 2-FCH H 303 11 2-F C—CF₃ H 371 12 3-F, 4-F C-(4-F—Ph) H 415 13 3-F, 4-FC—Ph H 397 14 3-F, 4-F C-(4-OMe—Ph) H 427 15 3-F, 4-F C-(3-F, 4-F—Ph) H433 16 3-F, 4-F C-(4-OCF₃—Ph) H 481 17 3-F, 4-F C—C₂F₅ H 439 18 2-F N Et352 19 3-F, 4-F N Et 336 20 2-F N Me 318 21 2-F, 5-F N Et 350 22 2-F N H304 23 3-F, 4-F N H 322 24 3-F, 4-F N CF₃ 390 25 2-F, 4-CF₃ N CF₃ 440 263-F, 4-F N CH₂CF₃ 404 27 2-F, 5-F N CH₂CF₃ 404 28 2-F CH CH₂Ph 393 292-F CH Ph 379 30 2-F, 4-CF₃ C—CF₃ H 439 31 2-F, 4-F, 5-F C—CF₂CF₃ H 37932 4-Br, 2-F, 5-F C—CF₃ H 467, 469 33 4-Br, 2-F, 5-F N CF₃ 468, 470

While the invention has been described and illustrated with reference tocertain particular embodiments thereof, those skilled in the art willappreciate that various adaptations, changes, modifications,substitutions, deletions, or additions of procedures and protocols maybe made without departing from the spirit and scope of the invention.For example, effective dosages other than the particular dosages as setforth herein above may be applicable as a consequence of variations inresponsiveness of the mammal being treated for any of the indicationswith the compounds of the invention indicated above. The specificpharmacological responses observed may vary according to and dependingupon the particular active compounds selected or whether there arepresent pharmaceutical carriers, as well as the type of formulation andmode of administration employed, and such expected variations ordifferences in the results are contemplated in accordance with theobjects and practices of the present invention. It is intended,therefore, that the invention be defined by the scope of the claimswhich follow and that such claims be interpreted as broadly as isreasonable.

1-40. (canceled)
 41. A method of treating low glucose tolerancecomprising administering to a mammalian patient in need of suchtreatment a therapeutically effective amount of a compound of theformula I:

wherein: Ar is phenyl which is unsubstituted or substituted with 1-5 ofR³, wherein R³ is independently selected from the group consisting of:(1) halogen, (2) C₁₋₆alkyl, which is linear or branched and isunsubstituted or substituted with 1-5 halogens, (3) OC₁₋₆alkyl, which islinear or branched and is unsubstituted or substituted with 1-5halogens, and (4) CN; X is selected from the group consisting of: (1) N,and (2) CR²; R¹ and R² are independently selected from the groupconsisting of: (1) hydrogen, (2) CN, (3) C₁₋₁₀alkyl, which is linear orbranched and which is unsubstituted or substituted with 1-5 halogens orphenyl, which is unsubstituted or substituted with 1-5 substituentsindependently selected from halogen, CN, OH, R⁴, OR⁴, NHSO₂R⁴, SO₂R⁴,CO₂H, and CO₂C₁₋₆alkyl, wherein the CO₂C₁₋₆alkyl is linear or branched,(4) phenyl which is unsubstituted or substituted with 1-5 substituentsindependently selected from halogen, CN, OH, R⁴, OR⁴, NHSO₂R⁴, SO₂R⁴,CO₂H, and CO₂C₁₋₆alkyl, wherein the CO₂C₁₋₆alkyl is linear or branched,and (6) a 5- or 6-membered heterocycle which may be saturated orunsaturated comprising 1-4 heteroatoms independently selected from N, Sand O, the heterocycle being unsubstituted or substituted with 1-3substituents independently selected from oxo, OH, halogen, C₁₋₆alkyl,and OC₁₋₆alkyl, wherein the C₁₋₆alkyl and OC₁₋₆alkyl are linear orbranched and optionally substituted with 1-5 halogens; R⁴ is C₁₋₆alkyl,which is linear or branched and which is unsubstituted or substitutedwith 1-5 groups independently selected from halogen, CO₂H, andCO₂C₁₋₆alkyl, wherein the CO₂C₁₋₆alkyl is linear or branched; or apharmaceutically acceptable salt thereof.
 42. A method of treating lowglucose tolerance comprising administering to a mammalian patient inneed of such treatment a therapeutically effective amount of a compoundof the formula:

or a pharmaceutically acceptable salt thereof.